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1.
Usually referred to as a NAR.
Pronounced: gnar as in the first half of gnarly

Def: When 2 people are seeing one another on a regular basis for a lengthy amount of time they usually can be give the title. This couple will act as if they are in a relationship, but will not call each other “boyfriend/girlfriend,” but may use pet names such as “honey, baby, snookums, ect”

This word can be used up to the extreme of 2 people cohabitating for many years, having kids, mixing bank accounts; at this point it would be referred as a Not A Marriage.
Patrick: Ruby and Zeph are always together, they are hanging out all the time. I think he is taking her to Thanksgiving dinner!
Sheena: So are they an item?
Patrick: No, its just a NAR (Not A Relationship)! I asked them about it last night.
by Bessie Lou November 05, 2009